| September 1939 | CO: |
| Sep 39 | North Irish Horse |
| 4/9/39 | Belfast Referring to WO Letter of 30th August, GOC NID proposes, amongst other things, that detachments or Squadrons be located as follows:-
| HQ and | one Sqn | ENNISKILLEN |
| | one Sqn | ARMAGH |
| | one Sqn | DUNGANNON |
Sir Basil Brooke Bt provisionally selected as Commanding Officer and the Secretary of County Antrim TA & AF Association issues instructions as regards selection of officers, men, recruiting, accommodation and courses of instruction. |
| 8/9/39 | Letter from War Office authorising reconstitution of the NIH. Regt will now be raised and equipped on War Establishment, Capt the Right Honourable Sir Basil Brooke, Bt DL, CBE, MP, to be commanding Officer and Capt OC Smith-Bingham, 17/21st Lancers appointed as Adjutant. Two regular and four TA NCOs will be despatched as PSIs. |
| 9/9/39 | Adjt reports to NID Victoria Bks. One SSgt and one Sgt posted as PSIs from Derbyshire Yeomanry. |
| 10/9/39 | Two Cpls posted as PSIs from East Riding Yeomanry. |
| 12/9/39 | Recce by Capt Smith-Bingham of suggested accommodation for Sqn in ENNISKILLEN, DUNGANNON and ARMAGH. |
| 15/9/39 | Temporary office opened in Victoria Bks, BELFAST. |
| 20/9/39 | Owing to his inability, for political duties, of Sir Basil Brooke to assume command, Major Sir Ronald Ross appointed CO and granted acting rank of Lt Col. |
| 21/9/39 | Lt The Earl of Erne RARO Royal Horse Guards posted to Regt as 2i/c and granted acting rank of Major. |
| 22/9/39 | Further recce of ENNISKILLEN (CASTLE BKS and COUNTY HALL), ARMAGH and GOSFORD CASTLE by the CO, Major Lord Erne and Adjt. |
| 24/9/39 | NID arranges that recruits will be accommodated and given an initial period of training with 1st Btn East Lancashire Regt at HOLYWOOD BKS BELFAST. |
| 26/9/39 | First 12 recruits enlisted. |